Retinoid-related orphan receptors (RORs) are transcription factors which belong to the steroid hormone nuclear receptor super family. The ROR family consists of three members, ROR alpha (RORα), ROR beta (RORβ) and ROR gamma (RORγ), also known as NR1F1, NR1F2 and NR1F3 respectively (and each encoded by a separate gene RORA, RORB and RORC, respectively). RORs contain four principal domains shared by the majority of nuclear receptors: an N-terminal A/B domain, a DNA-binding domain, a hinge domain, and a ligand binding domain. Each ROR gene generates several isoforms which differ only in their N-terminal A/B domain. Two isoforms of RORγ, RORγ1 and RORγt (also known as RORγ2) have been identified.
RORγt is a truncated form of RORγ, lacking the first N-terminal 21 amino acids and is exclusively expressed in cells of the lymphoid lineage and embryonic lymphoid tissue inducers (Sun et al., Science, 2000, 288, 2369-2372; Eberl et al., Nat Immunol., 2004, 5: 64-73) in contrast to RORγ which is expressed in multiple tissues (heart, brain, kidney, lung, liver and muscle).
RORγt has been identified as a key regulator of Thl7 cell differentiation. Thl7 cells are a subset of T helper cells which produce IL-17 and other proinflammatory cytokines and have been shown to have key functions in several mouse autoimmune disease models including experimental autoimmune encephalomyelitis (EAE) and collagen-induced arthritis (CIA). In addition, Thl7 cells have also been associated in the pathology of a variety of human inflammatory and autoimmune disorders including multiple sclerosis, rheumatoid arthritis, psoriasis, Crohn's disease and asthma (Jetten et al., Nucl. Recept. Signal, 2009, 7:e003; Manel et al., Nat. Immunol., 2008, 9, 641-649). The pathogenesis of chronic autoimmune diseases including multiple sclerosis and rheumatoid arthritis arises from the break in tolerance towards self-antigens and the development of auto-aggressive effector T cells infiltrating the target tissues. Studies have shown that Thl7 cells are one of the important drivers of the inflammatory process in tissue-specific autoimmunity (Steinman et al., J. Exp. Med., 2008, 205: 1517-1522; Leung et al., Cell. Mol. Immunol., 2010 7: 182-189). Thl7 cells are activated during the disease process and are responsible for recruiting other inflammatory cells types, especially neutrophils, to mediate pathology in the target tissues (Korn et al., Annu. Rev. Immunol., 2009, 27:485-517) and RORγt has been shown to play a critical role in the pathogenic responses of Thl7 cells (Ivanov et al., Cell, 2006 126: 1121-1133). RORγ t deficient mice have shown no Thl7 cells and also resulted in amelioration of EAE. The genetic disruption of RORγ in a mouse colitis model also prevented colitis development (Buonocore et al., Nature, 2010, 464: 1371-1375). The role of RORγt in the pathogenesis of autoimmune or inflammatory diseases has been well documented in the literature. (Jetten et al., Adv. Dev. Biol., 2006, 16:313-355; Meier et al. Immunity, 2007, 26:643-654; Aloisi et al., Nat. Rev. Immunol., 2006, 6:205-217; Jager et al., J. Immunol., 2009, 183:7169-7177; Serafmi et al., Brain Pathol., 2004, 14: 164-174; Magliozzi et al., Brain, 2007, 130: 1089-1104; Barnes et al., Nat. Rev. Immunol., 2008, 8: 183-192).
In addition, RORγt has also been shown to play a crucial role in other non-Thl7 cells, such as mast cells (Hueber et al., J Immunol., 2010, 184: 3336-3340). RORγt expression and secretion of Thl7-type of cytokines has also been reported in NK T-cells (Eberl et al., Nat. Immunol., 2004, 5: 64-73) and gamma-delta T-cells (Sutton et al, Nat. Immunol., 2009, 31: 331-341; Louten et al., J Allergy Clin. Immunol., 2009, 123: 1004-1011), suggesting an important function for RORγt in these cells.
Respiratory disorders related to airway inflammation include a number of severe lung diseases including asthma and COPD (Chronic Obstructive Pulmonary Diseases). The airways of asthmatic patients are infiltrated by inflammatory leukocytes, of which the eosinophil is believed to be the most prominent component. Inflammatory sensitization of airway neurons is believed to increase nasal sensitivity, heighten the sense of irritation, and promote fluid secretion, airway narrowing, and bronchoconstriction. Oxidative stress is a hallmark of most acute and chronic inflammatory airway conditions, including viral infections, asthma, rhinitis, and COPD.
Asthma and COPD are major chronic diseases related to airway obstruction. The Global Initiative for Chronic Obstructive Lung Disease provides guidelines for the distinction between asthma and COPD. Asthma is believed to be a chronic inflammatory disease wherein the airflow limitation is more or less reversible while it is more or less irreversible in the case of COPD. Asthma among other things is believed to be triggered by inhalation of sensitizing agents (like allergens) unlike noxious agents (like particles and certain gases) in the case of COPD. Though both are believed to have an inflammatory component, the inflammation in asthma is believed to be mostly eosinophilic and CD-4 driven, while it is believed to be mostly neutrophilic and CD-8 driven in COPD. Emphysema is a type of COPD in which tiny air sacs in the lungs—alveoli—fill up with air. As the air continues to build up in these sacs, they expand, and may break or become damaged and form scar tissue. The patient becomes progressively short of breath.
PCT Publication Nos. WO 2012/139775, WO 2012/027965, WO 2012/028100, WO 2012/100732, WO 2012/100734, WO2012/064744 and WO 2013/171729 disclose heterocyclic compounds which are modulators of retinoid-related orphan receptor gamma (RORγ) receptor activity.
We have surprisingly found that RORγ inhibitors, which have high potency (e.g., IC50 for inhibiting human RORγ receptor activity of less than 2 micromolar) are effective in the treatment of respiratory disorders when administered to a subject by an inhalation route, for example, by in-mouth or intranasal administration.